I'm not Eclipse user neither IntelliJ. I tried IntelliJ after looking at this post. First impression, InteliJ interface is lot better and cleaner than Eclipse. Eclipse interface (or skin) looks ugly and takes lot of space with its big toolbar buttons and rounded tabs. Also I noticed that IntelliJ shows shortcuts while hovering over things (like completion, docks etc...) nicely, which is pretty cool.

Rest I can't comment on how good they are with enhancing your productivity, as I never used them.